Telecommunication systems



May 26, 1959 A. DAVISO N T L TELECOMMUNICATION SYSTEMS Original Filed Jan. 12, 1958 VKSO ALAN DAV/SON. RONALD THREADGOLD.

Inventors United States Patent TELECOMIVIUNICATION SYSTEMS Alan Davison and Ronald Threadgold, Liverpool, England, assiguors to Automatic Telephone & Electric Company Limited, Liverpool, England, a British com- P Original application January 12, 1958, Serial No. 330,638. Divided and this application February 26, 1957, Serial No. 642,461

7 Claims. (Cl. 31584.5)

This application is a division of co-pending application Serial No. 330,638, filed on January 12, 1953.

The present invention relates to two-position circuit devices and is more particularly concerned with such circuit devices which operate at high speeds.

The main object of the invention is to provide an improved high-speed two-position circuit device which has many applications in the field of automatic telephony.

According to one feature of the invention, a two-position circuit device comprises two gas discharge tubes so arranged that in the presence of a control potential one of said tubes is primed while the second is backed-0E while in the absence of said control potential the second tube only is primed whereby a pulse applied to both tubes causes one or other of the tubes to strike according to the presence or absence of said control potential.

According to another feature of the invention, a two-.

position circuit device comprises two gas discharge tubes, a pulse source connected in parallel to the trigger electrodes of both tubes, a lead connected in parallel to the trigger electrode of one tube and the cathode of the second tube and a source of biasing potential permanently connected to the trigger electrode of said second tube whereby the application of a pulse from said pulse source to the trigger electrodes of both tubes causes one or other of said tubes to strike according to the presence or absence of a control potential on said lead.

The invention will be better understood from the following description taken in conjunction with the accompanying drawing which forms part of Fig. 6 of the drawings accompanying copending application Serial No. 330,- 638 from which the present application is divided.

The circuit shown in the drawing illustrates a hunting circuit for taking into use the first idle one of a plurality of pieces of equipment. The circuit consists of a plurality of similar stages, one for each piece of equipment. For convenience, however, the drawing only shows the first and last stage. The first stage comprises the three tubes VK20, VK21 and VK22 while the last stage similarly arranged tubes VK30, VK31 and VK32. Leads such as 20 and 30 extendindividually to the pieces of equipment and if the latter are available,va positive potential is applied to the associated lead. Thus if the equipment associated with lead 20 is available, the positive potential thereon will serve to bias the tube VK20. When the hunting operation is to take place, a pulse is applied to lead 22, which is connected via capacitors such as C20 and C30. Those tubes strike which are positively biased over the lead such as 20 and it will first be assumed that the equipment associated with lead 20 is available. Tube VK20 will therefore strike and a positive voltage will be developed at the junction of the two cathode resistors R20 and R21. Resistor R21 forms, together with resistor R22, the cathode load of tube VK21 so that the positive voltage at the junction of resistors R20 and R21 serves to back 011" tube VK21. The same positive voltage, however, serves to apply via resistor R23 a positive biasing potential to the trigger electrode of tube 2,888,612 Patented May 26,

VK22. In addition when tube VK20 strikes it causes the diode VN20 to strike whereby a positive potential is applied from resistor R24 to the pulse delay circuit which then applies a delayed pulse to the trigger electrodes of tubes VK21 and VK22. Only tube VK22 strikes, however, since tube VK21 is backed off as described above. Tube VK22 in striking applies a positive potential to lead 21 which is connected to the associated piece of equipment and this positive potential serves to take into use the piece of equipment whereupon the positive potential is removed from lead 20. When the piece of equipment has been taken into use, means (not shown) become effective to extinguish the conducting tubes in the hunting circuit.

Now assume that the piece of equipment associated with lead 20 is unavailable when the hunting operation is initiated but that at least one of the other pieces of equipment is available. When the hunting operation is initiated, tube VK20 will not strike but at least one of the tubes corresponding to VK20 and which is associated with an available piece of equipment will strike so that a positive potential is developed in resistor R24 on the striking of the associated diode. The pulse applied by the pulse delay circuit PD to the tubes VK21 and VK22 now causes tube VK21 to strike since this tube is not backed off but tube VK22 does not strike since no positive biasing potential is applied to its trigger electrode. Tube VK21 in striking applies a positive pulse to the two tubes of the next stage which corresponds to tubes VK21 and VK22 of the first stage. One or other of these tubes will strike according to the condition of the associated piece of equipment and if it is available, it will be taken into use while if it is unavailable a pulse will be repeated to the next stage. piece of equipment is found.

We claim:

1. A two-position switching-circuit arrangement comprising first and second gas-filled discharge tubes each provided with at least an anode, a cathode and a trigger electrode, an input lead connected to both said first and second tubes, means for applying a pulse to said input lead, a first output lead connected to said first tube, a second output lead connected to said second tube a source of positive priming potential connected only to the trigger electrode of said first tube, a biasing lead connected to the cathode of said first tube and to the trigger electrode of said second tube and means for applying a positive potential to said biasing lead whereby on the application of a pulse to said input lead in the absence of a positive potential on said biasing lead said first tube only strikes to apply a potential to said first output lead and on the:

application of a pulse to said input lead in the presence put lead. 1

2.. A changeover circuit arrangement comprising first and second gas-filled discharge tubes each provided with at least an anode, a cathode and a trigger electrode, a cathode resistor for each tube, an input lead connected to the trigger electrodes of said first and second tubes, means for applying a positive-going pulse to said input lead, a source of priming voltage connected to the trigger electrode of said first tube whereby the application of a positive-going pulse to said input lead causes the striking of said first tube only, a biasing lead connected to the cathode of said first tube and to the trigger electrode of said second tube, means for applying a positive potential to said biasing lead thereby to back 011. said first tube and prime said second tube whereby the application of a positive-going pulse to said input lead causes the striking of said second tube only.

3. A two-position switching-circuit arrangement com- This operation continues until an idle prising first and second gas-filled discharge tubes each provided with at least an anode, a cathode and a trigger electrode, an input lead connected to the trigger electrodes of both said first and second tubes, means for applying a positive pulse to said input lead, a first output lead connected to the cathode of said first tube, a second output lead connected to the cathode of said second tube, a source of positive priming potential connected only to the trigger electrode of said first tube, a biasing lead connected to the cathode of said first tube and to the trigger electrode of said second tube and means for applying a positive potential to said biasing lead whereby on the application of a positive pulse to said input lead in the absence of a positive potential on said biasing lead said first tube strikes due to the priming potential applied to the trigger electrode thereof, said first tube in striking serving to apply a positive potential to said first output lead and on the application of a positive pulse to said input lead in the presence of a positive potential on said biasing lead said first tube is backed off by the positive potential on said biasing lead and said second tube strikes due to the positive potential on said biasing lead, said second tube in, striking serving to apply a positive potential to said second output lead.

4. Circuit arrangements comprising a plurality of serially-connected stages each consisting of first and second gas-filled discharge tubes having at least an anode, a cathode and a trigger electrode, an input lead connected to the trigger electrodes of both said first and second tubes of said first stage, a source of priming voltage connected to the trigger electrodes of the first tubes of all said stages, a plurality of biasing leads individually connected to the cathode of the first tube and the trigger electrode of the second tube of each of said stages, means for applying a positive potential to at least one of said biasing leads, a plurality of output leads connected to the cathodes of the second tubes of all said stages and a pulse repeating lead connected between the first tube in one stage and the first and second tubes of the next stage whereby the application of a positive pulse to said input lead causes the positive pulse to be repeated to the second stage due to the striking of the first tube of said first stage in the absence of a positive potential on the biasing lead of said first stage, the positive pulse being repeated from stage to stage until a stage is reached where a positive potential is applied to the biasing lead thereof whereupon due to the striking of the second tube of said last-mentioned stage in response to the positive pulse a positive potential is applied to the output lead of said last-mentioned stage.

5. Circuit arrangements comprising a plurality of serially-connected stages each consisting of first and second gas-filled discharge tubes, a plurality of output circuits each associated with one of said second gas-filled discharge tubes, an output circuit connected from each of said first tubes in each stage to apply an actuating pulse to both tubes of the next succeeding stage; a first source of priming potential connected to said first tubes, means for connecting concurrently a second source of priming potential to said second tubes and a source of backing-oft potential to said first tubes and means for applying a pulse to the first and second tubes of said first stage whereby the first tube of the first stage strikes to repeat the pulse to the next stage in the absence of the second priming potential and backing-01f potential while the second tube of the first stage strikes to repeat the pulse over the associated outlet in the presence of the second priming potential and backing-ofi potential.

6. A two-position switching-circuit arrangement comprising first and second gas-filled discharge tubes, each of said tubes having at least an anode, a cathode, and a trigger electrode, first and second output circuits, connected respectively to be completed by discharge between the anodes and cathodes of said first and second tubes, an input pulse lead connected to both of said tubes to apply thereto simultaneously an actuating pulse between the respective cathodes and trigger electrodes to drive said trigger electrodes in the positive direction with respect to said cathodes, biasing means connected to both of said tubes for applying normally a priming potential between the trigger electrode and cathode of said first tube to facilitate the striking thereof upon the application of an actuating pulse and a hold ofl potential between the trigger electrode and cathode of said second tube to prevent its striking on application of such actuating pulse, and means including a biasing connection for reversing the priming and hold-off potentials applied to said respective tubes upon the application of a potential to said biasing lead from a source external to said switching circuit.

7. A two-position circuit arrangement comprising first and second gas-filled discharge tubes each having at least a cathode, an anode and a trigger electrode, first and second output circuits connected respectively to be completed by discharge between the anodes and cathodes of said first and second tubes, an input pulse circuit connected to apply actuating pulses simultaneously to both of said tubes to drive the trigger electrodes thereof in the positive direction with respect to the cathodes thereof to tend to cause discharge thereof upon the application of such actuating pulses, means for applying a positive priming potential to the trigger electrode of said first tube only, to cause it to strike on application of such actuating pulse, and a biasing circuit including a resistor network connecting to the cathode of said first tube and the trigger electrode of said second tube to apply positive potentials to both, thereby applying a holdoff potential to said first tube to prevent completion of said first output circuit and a priming potential to said second tube to cause completion of said second output circuit upon application of such actuation pulse when said biasing circuit is energized.

References Qited in the file of this patent UNITED STATES PATENTS 2,758,250 Ridler et al. Aug. 7, 1956 2,765,426 Faulkner Oct. 2, 1956 2,805,363 Baker et al. Sept. 3, 1957 2,810,098 Pearce et al. Oct. 15, 1957 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 2,888,612 May 26, 1959 Alan Da rison et .al; It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as cor I In the heading to the drawing, line 3, for "Jan 12, 1958" read Jan. 12, 1953 in the heading to the printed specification, line '7, for "January 12, 1958" read January 12, 1953 ='-=-o Signed and sealed this 3rd day of May 1960.a

Attest:

KARL H. AXLINE ROBERT c. WATSON Attesting Officer I Conmissioner of Patents 

